Disclosed in the embodiments herein is an improved system for accurately maintaining the correct lateral position for imaging of rotating xerographic photoreceptor belts or other printing system image bearing belts, including intermediate image transfer belts, with various advantages over prior such so-called xe2x80x9cbelt tracking systemsxe2x80x9d or the like, as explained herein.
In particular, there is disclosed in the embodiments herein an improved, low cost and simple system for accomplishing the above and other advantages. Improved photoreceptor and/or intermediate belt tracking is particularly desirable to reduce lateral registration errors between color separations in color printing. In these embodiments the belt lateral position is sensed and automatically controlled by belt edge guides, but the belt edge guides do not have fixed positions. Instead of fixing their positions, the belt edge guides act on the belt edges with a relatively constant and low lateral force, the low level of which force may be adjusted slowly, but is sufficient to maintain the belt in the desired average lateral position. The magnitude of the maximum applied belt edge force is low as compared to other belt edge guide belt control systems. This reduces belt wear, etc. Yet, belt profile induced belt rotation fluctuations can also be significantly reduced. Belt rotation fluctuations can introduce mixed color printing skew registration errors.
With the addition of an extra color to a printer, even for a black and white printer, color-to-black registration became an important issue. The latent image for black and color may be generated at different (opposite parts) of the belt. Therefore, accurate belt tracking is important to ensure color-to-black registration. However, the advantages of the belt tracking system of the disclosed embodiment are also applicable for full color printing and many other belt tracking applications. Those relative advantages over some other belt tracking systems can include lower cost as compared to active (power driven) steering systems, with no induced belt skew, and substantially less edge force (as well as no induced belt skew) as compared to conventional belt edge guide systems. This can increase belt life significantly.
Furthermore, the disclosed embodiments are more easily retrofitted as an improvement in existing printers than are active steering or roller pivoting steering systems. In particular, the disclosed embodiment can more easily enable the conversion of a single color (black only) printer to a highlight color machine with less change to the photoreceptor mounting or module.
The disclosed embodiments can even accomplish the accurate maintaining of a substantially constant lateral belt position with only a simple low applied spring force system, of a low force level which may be set to only slightly above the force level needed to overcome the average force required to overcome the other steering effects of the belt system (i.e. the mechanical errors induced by the belt""s plural mounting rollers, etc.).
By way of background, various types of prior xe2x80x9cbelt tracking systemsxe2x80x9d and belt edge guides are known in the art for maintaining and controlling the position of rotating xerographic photoreceptor belts, including lateral belt guidance to obtain good color registration in color printing. The following Xerox Corporation U.S. patent disclosures are noted by way of some examples, in particular, U.S. Pat. No. 5,383,006 issued Jan. 17, 1995 to V. Castelli; U.S. Pat. No. 5,316,524 issued May 31, 1994 to C. Wong, et al, and also U.S. Pat. No. 6,195,518; 5,233,388; and 5,467,171.
Many of the prior belt tracking systems, such as disclosed in said U.S. Pat. No. 6,195,518 or in Xerox Corporation U.S. Pat. No. 4,061,222, 4,174,171, 4,344,693, 4,572,417, or 4,961,089, use active belt roller axis pivoting or xe2x80x9ctiltingxe2x80x9d systems. However, these tend to add complexity and cost, among other issues as noted herein.
A specific feature of the specific embodiments disclosed herein is to provide a printing method in which a rotatable print image bearing belt is mounted on at least one axial belt roller, and said rotatable print image bearing belt must be maintained in a desired substantially consistent lateral registration to maintain image quality; the lateral misregistration of said rotatable print image bearing belt is sensed and a low and substantially constant lateral positional corrective force is applied to said rotatable print image bearing belt, in response to said sensing of said lateral misregistration of said rotatable print image bearing belt, in one of the two directions axial of said axial belt roller, for at least one complete rotation of said rotatable print image bearing belt, said substantially constant transverse corrective force having a force level sufficient to provide said desired substantially consistent lateral registration of said print image bearing belt.
Further specific features disclosed in the embodiments herein, individually or in combination, include those wherein said low and substantially constant lateral positional corrective force is applied in the same direction for plural said rotations of said image bearing belt; and/or wherein said low and substantially constant lateral positional corrective force is applied indirectly through a low spring constant spring system; and/or wherein said low and substantially constant lateral positional corrective force is applied by a servo system with a low bandwidth corresponding to plural said rotations of said image bearing belt; and/or wherein said spring system has first and second spring components, and further including a reversible and low bandwidth drive motor acting with more force on said first spring component than said second spring component to provide said low and substantially constant lateral positional corrective force; and/or wherein said low and substantially constant lateral positional corrective force is applied indirectly through a low spring constant spring system, wherein said spring system has first and second spring components, and further including a reversible and low bandwidth drive motor acting with more force on said first spring component than said second spring component to provide said low and substantially constant lateral positional corrective force; and/or wherein said print image bearing belt is mounted on said at least one axial belt roller between first and second non-rotating belt edge guides, and said low and substantially constant lateral positional corrective force is applied to at least one of said first and second non-rotating belt edge guides; and/or wherein said first and second non-rotating belt edge guides are connected together by a linking system for common lateral movement in the axial direction of said axial belt roller, and said low and substantially constant transverse positional corrective force is applied thereto; and/or a printing apparatus in which a rotatable print image bearing belt is mounted on at least one axial belt roller, and said print image bearing belt must be maintained in a desired substantially consistent lateral registration to maintain image quality, the improvement comprising means for sensing lateral misregistration of said rotatable print image bearing belt, and means for applying a low and substantially constant lateral positional corrective force to said image bearing belt in the axial direction of said axial belt roller for more than a complete rotation of said image bearing belt, said substantially constant lateral positional corrective force having a force level sufficient to maintain said desired substantially consistent lateral registration of said rotatable print image bearing belt; and/or wherein said rotatable print image bearing belt is mounted on said at least one axial belt roller between first and second non-rotating belt edge guides, and said low and substantially constant lateral positional corrective force is applied to at least one of said first and second non-rotating belt edge guides; and/or wherein said first and second non-rotating belt edge guides are connected together by a linking system for common lateral movement in the axial direction of said axial belt roller, and said low and substantially constant transverse positional corrective force is applied thereto.
The terms xe2x80x9creproduction apparatusxe2x80x9d or xe2x80x9cprinterxe2x80x9d as used herein broadly encompasses various printers, copiers or multifunction machines or systems, xerographic or otherwise, unless otherwise defined.
As to specific components of the subject apparatus or methods, or alternatives therefor, it will be appreciated that, as is normally the case, some such components are known per se in other apparatus or applications, which may be additionally or alternatively used herein, including those from art cited herein. For example, it will be appreciated by respective engineers and others that many of the particular components, component mountings, etc., illustrated or described herein are merely exemplary, and that the same novel motions and functions can be provided by other known or readily available alternatives. All cited references, and their references, are incorporated by reference herein where appropriate for teachings of additional or alternative details, features, and/or technical background. What is well known to those skilled in the art need not be described herein.